Single DB or Multiple in SaaS?

I’m creating a SaaS at the moment that will have various companies subscribed. All data for each company should be entirely separate. I’m wondering what the best practice here is?

  1. A single instance and DB using a companyId field to denote who the data belongs to and tight controls in the publications.
  2. An instance per company that connects to the Mongo deployment with different DBs for each company. Using something like this db-proxy.

Load and data size is likely to be low so I’ve been thinking of 1, but 2 seems the more secure option - although setup for each company is a bit more work. Thoughts?